This invention relates generally to rotary inking devices for use in apparatus for applying printed indicia upon a moving line of articles and in particular, is concerned with the provision of an inking wheel having an relatively firm outer ring of inking material mounted upon a radially yieldable support assembly whereby a constant pressure may be exerted upon the inking material without deterioration thereof materially to extend the useful life of said ring.
Conventional inking wheels, such as utilized with apparatus for imprinting linearly moving packages, carry ink absorbent circumferential surfaces formed of sponge or foam materials to which printing ink is applied from ink reserviors at the time of use. Microporous rings pre-impregnated with printing ink also are conventional and are capable of being used without ink reserviors and applicators. Generally, the use of the microporous members carrying their own supply of ink has gained substantial commercial acceptance. The ink is held in suspension within the ring material and flows instantly to the circumferential surface of the ring when needed by engagement with the type surface or transfer roller of the imprinting apparatus.
Notwithstanding the advantages of using pre-inked inking members, difficulties have been encountered which limit their use. The outer circumferential surface of the pre-inked rings often generally is formed of a relatively high density, hard surfaced material which does not permit the type to be sufficiently impressed so that the application of ink thereto may be less effective than would be the case if foam or spongy material were used. Further, in the case of the pre-inked microporous plastic material, as the ink content is reduced during use, the roll diameter decreases as a result of the cellular structure of the ring collapsing or shrinking. Adjustment devices must be utilized and these are often expensive, such as when camming arrangements must be provided to adjust the position of the inking wheel relative to the imprinting wheel carrying the type faces. It would be more expedient and less expensive to utilize spring biasing rather than camming arrangements but pressure contact involved would be likely materially to reduce the useful life of the inking ring. Use of adjustment screws would not be feasible because continuous monitoring by the operator is required.
Accordingly, it would be desirable to provide an inking wheel having an inking surface which is capable of being driven pressed against the circumferential surface of an imprinting wheel without reducing the useful life of the inking wheel.